We moved a client off of on prem exchange to Office 365 this past weekend. When I arrived out there Friday, I exported their mailbox (Full Mailbox, all folders included) to a PST file. Once I got their O365 software installed, I connected their mailboxes and transferred their mail. Each user only had, at most, 100MB of mail so we’re not dealing with a ton of mail here.
Anyway, I noticed today that their contacts appear to be non-existent. Like they didn’t get exported when I did the initial export of the full mailbox.